Peplomycin-induced apoptosis in oral squamous carcinoma cells depends on bleomycin sensitivity

Oral squamous carcinoma cell line SSCKN cells were shown to be highly sensi tive to bleomycin, whereas SCCTF cells were minimally sensitive to this rea gent. To determine whether the anticancer drug resistance to oral squamous carcinoma cells could be related to the degree of the drug-induced apoptosi s, we examined the effects of peplomycin on induction of apoptosis in these cells. After reaching subconfluence, SCCKN and SCCTF cells were exposed to various concentrations of peplomycin. Peplomycin caused cytotoxicity in bo th SCCKN and SCCTF cells in a dose-dependent fashion with the maximal effec t at concentrations of 1 and 10 muM, respectively, as determined by phase-c ontrast microscopy and WST-1 cell viability assay. By using the Hoechst 333 42 staining, we observed marked nuclear condensation and fragmentation of c hromatin in SCCKN cells treated with 1 muM peplomycin. How ever, SCCTF cell s treated with 1 muM peplomycin showed neither nuclear condensation nor fra gmentation. DNA ladder formation was also detected in both cell lines by tr eatment with peplomycin. The induced DNA ladder formation in SCCKN and SCCT F cells was dose-dependent, with the maximal effect at concentrations of 5 and 50 muM, respectively. Bleomycin also induced DNA ladder formation in SC CKN and SCCTF cells with different sensitivities. Mitomycin C induced DNA l addering in both SCCKN and SCCTF cells; however, the intensity of DNA ladde r formation was almost the same in both cell lines. The present results ind icate that peplomycin-induced apoptosis in oral squamous carcinoma cell lin es depends on the sensitivity of these cells to bleomycin. (C) 2001 Elsevie r Science Ltd. All rights reserved.